1. Field of the Invention
The present invention relates to a method and an apparatus for manufacturing semiconductor devices such as a semiconductor substrate and a liquid crystal substrate. More particularly it relates to a method and an apparatus for treating the substrate with processing, equipped with a function of performing in-situ measurement of foreign materials in a processing chamber (a vacuum processing chamber) and the state of contamination of the processing chamber where the processing such as thin film growth (film formation) and etching is conducted.
2. Description of the Related Art
Processing that utilizes a plasma is widely applied to Semiconductor manufacturing processes and manufacturing processes of substrates for liquid crystal display devices as in the form of an etching apparatus or others.
For the processing apparatuses like the above that use the plasma, it is known that reaction products generated, for example, by an etching reaction exerted by the plasma processing are deposited on walls and/or electrodes in a plasma processing chamber. This deposit may peel off with the passage of time and become suspended foreign materials. These suspended foreign materials fall on a wafer to become adhesion foreign materials at the moment when the etching process is ended and the plasma discharge is stopped. This brings about malfunctioning properties of a circuit and defective pattern appearance to thereby decrease the yield and reduce the reliability on a semiconductor device.
Many apparatuses for inspecting the foreign materials adhering to the surface of an in-process substrate such as a wafer have been reported and some of which have been actually used. These are types such as to inspect the in-process substrate temporarily taken out from the plasma processing apparatus, and however suffer from following problem: when a number of foreign materials are found generated, the other wafers in the same lot have already undergone the processing. This leads to a mass generation of the defectives, decreasing the yield. In addition, even at the evaluation after the processing, those apparatuses can not cover distributions of the foreign materials and their changes with the lapse of time. Therefore, a technology of manufacturing semiconductors and liquid crystals needs in-situ monitoring of the state of contamination in the processing chamber. The size of the suspended foreign material in the processing chamber ranges from a few sub-micrometers to a few hundred μm. In the field of semiconductors where a degree of integration goes even higher, from 256 Mbit DRAM (Dynamic Random Access Memory) to 1 Gbit DRAM, the minimum line width of the circuit pattern is on a trend of approaching finer dimensions, say 0.25–0.18 μm, and accordingly the size of the foreign materials that must be detected is required to be as small as a few sub-micrometers.
The prior arts for monitoring the foreign materials suspended in the processing chamber (vacuum chamber) such as the plasma processing chamber are described in JP-A Nos. 118630/1982 (prior art 1), 25355/1991 (prior art 2), 147317/1991 (prior art 3), 82358/1994 (prior art 4), 124902/1994 (prior art 5), 213539/1998 (prior art 6), 251252/1999 (prior art 7), and 330053/1999 (prior art 8).
The prior art 1 discloses an evaporation apparatus equipped with a means for projecting a parallel beam having a different spectrum from that of the spontaneous emission light in a reaction space and a means for detecting scattered light from particulates generated in the space that are subjected to irradiation of the parallel beam.
The prior art 2 discloses a fine-particle measuring apparatus for measuring fine particles adhering to the surface of a semiconductor device substrate and suspended fine particles by means of a laser light scattering. The apparatus comprises: a laser light phase modulator part for generating two laser beams that have the same wavelength and were modulated by two signals of a predetermined frequency, having predetermined phases different to each other; an optical system for making the two laser light beams to intersect in a space containing fine particles that are subjects of the above measurement; an optical detecting part for receiving light scattered by fine particles that are subjects of the measurement in an area where the two laser light beams are made to intersect with each other and for converting the light into an electric signal; and a signal processing part for extracting a signal component, from among electric signals caused by this scattered light, whose frequency is either the same as or twice as much as that of the phase modulated signal at the laser light phase modulator part and such that its phase difference with respect to the phase modulated signal is temporally constant.
The prior art 3 describes a technology that includes the steps of: projecting coherent light into a reaction vessel in a scanning manner to generate light that scatters therein; and detecting light that scatters in the reaction vessel; and whereby the state of contamination of the reaction vessel is measured by means of analysis of the scattered light obtained by these steps.
The prior art 4 describes a particle detector comprising: scanning means for scanning an area in a reaction chamber of a plasma processing tool containing particles to be observed with the laser light; a video camera for generating a video signal of the laser light that has been scattered by the particulates in the area; and a means for processing and displaying the image of the video signal.
The prior art 5 describes a plasma processing apparatus comprising: a camera device for observing a plasma generation area in a plasma processing chamber; a data processing part for processing images obtained by the said camera device to obtain target information; and a control part for controlling at least one of exhaust means, process-gas introducing means, high-frequency voltage applying means, and purge-gas introducing means so that particles can be reduced in number based on the information obtained by the said data processing part.
The prior art 6 describes a small particulate sensor that comprises (1) a detector including: (a) a light emitter for emitting a light beam that traverses and irradiates a measurement volume, (b) an optical detector, and (c) an optical system for collecting scattered light from the measurement volume and directing the light to the optical detector, wherein the detector is configured to generate a signal that indicates the intensity of the light directed to the optical detector, and (2) signal processing means including: (e) a pulse detector that is interconnected with the optical detector so as to analyze the signal sent from the optical detector and detects pulses in the signals from the optical detector, and (f) an event detector for identifying a series of pluses that correspond to particulates and result from scattered light caused by the particulates in association with plural times of irradiation scans by the beam during when the particulates move in the measurement volume. Furthermore, the prior art 7 discloses a composition of a plasma suspension foreign-material measuring apparatus that is a plasma processing apparatus for generating a plasma in the processing chamber and treating the object to be processed with the said plasma, the apparatus comprising: an irradiation optical system, for projecting light that has a desired wavelength and has been intensity-modulated by the desired frequency into the processing chamber; scattered-light detecting optical system for separating the scattered light obtained from the processing chamber into the desired wavelength components and receiving them to effect their conversion into signals; and foreign-object signal extracting means for separating the signal indicating the suspended foreign material in the plasma or in its vicinity to effect detection by extracting a component of a desired frequency at which the intensity modulation has been performed from the signal obtained by the said scattered-light detecting optical system. Furthermore, the prior art 8 discloses a composition of a plasma suspension foreign-material measuring apparatus that is a plasma processing apparatus for generating a plasma in the processing chamber and treating the object to be processed with the said plasma, the apparatus comprising: an irradiation optical system for projecting a plurality of light beams that have mutually different wavelengths and were intensity-modulated by a desired frequency into the processing chamber; a scattered-light detecting optical system for separating the scattered light into a plurality of wavelength components whose wavelengths are mutually different and for receiving and converting them into plural signals; and foreign-material signal extracting means for separating the signal indicating the suspended foreign material in the plasma or in its vicinity to effect detection by extracting a component of a desired frequency at which the intensity modulation has been performed from the signal obtained by the said scattered-light detecting optical system.
Note that in the prior arts 1–6, the apparatuses are configured so as to project laser light into the plasma processing chamber through an observation window provided on a side thereof and detect the forward scattered laser light or lateral scattered laser light from an observation window that is discrete from the laser irradiation observation window and has been provided on an opposing side or other sides. Therefore, in these schemes that detect the forward scattered light or the lateral scattered light, the irradiation optical system and the detection optical system are constructed in discrete units, hence two observation windows for which these optical systems are installed, respectively, are necessary, and optical axis alignment needs to be conducted for the irradiation optical system and for the detection optical system, respectively; consequently their handling is troublesome.
In addition, normally, almost any models of the apparatus are equipped with the observation window provided on a side of the processing chamber such as the plasma processing chamber with the intention to monitor plasma emission, but it is quite many cases where only one observation window is provided. Therefore, there is a problem that any conventional technique that requires two observation windows cannot be applied to manufacturing equipment equipped with only one observation window.
In the conventional schemes whereby the forward scattered light or the lateral scattered light is detected, if the operator intends to scan the irradiation beam that is to be projected into the plasma processing chamber rotationally so as to observe a state of foreign material generation on the whole surface of the in-process substrate such as a wafer, a number of observation windows and detection optical systems are needed, which introduces a cause of considerable increase in cost, and it is also anticipated that, from a practical pint of view, it is extremely difficult to provide a number of observation windows and the detection optical systems because of constraints of a space factor.
On the other hand, in the field of semiconductor devices where a trend of higher packing densities toward 256 Mbit DRAM and even further toward 1 Gbit DRAM has been taking place, the minimum line width of the circuit pattern goes to thinner dimensions such as 0.25–0.188 μm, and accordingly the size of the foreign materials that must be detected is required to be as small as sub-micrometers. However, the prior arts 1–6 are limited to applications to observe comparatively large foreign materials because of difficulty in separating the foreign-material scattered light from the plasma emission, and it is considered to be difficult to detect minute foreign materials of the order of sub-micrometers.
In the prior arts 7–8, a problem of how to detect the foreign materials suspended in the plasma or in its vicinity is described, but a problem of how to detect the status of contamination of the foreign materials adhering to or deposited on the inside wall of the plasma processing chamber is not considered.